The invention relates to a trocar sleeve or cannula with a proximal main body having an axial through opening and with a distal sleeve connected to the main body.
Trocar sleeves of this type are generally known in endoscopic surgery. The trocar sleeves have an essentially one-piece construction, a cylindrical sleeve being soldered or bonded onto or into the proximal main body. The latter, which is the most complicated and therefore cost-intensive part of the trocar sleeve, generally has connections for surgical or optical appliances and gas supplies. It is also standard practice to have a manually adjustable or automatically closing valve for preventing a gas exchange between the interior of the body and the external atmosphere.
These trocar sleeves are traversed by a conically tipped or pointed trocar and are then inserted into the interior of the body, e.g. by perforating the abdominal wall. The trocar sleeve tip is bevelled, so that there is a lower perforation resistance on perforating the abdominal wall. After inserting the distal end of the trocar sleeve into the interior of the body, the trocar is withdrawn from the trocar sleeve, so that the latter constitutes a closable opening with respect to the body interior, through which it is possible to introduce into the latter optical or surgical instruments. Often trocar sleeves are provided with a connection for a gas supply, particularly CO.sub.2, so as to raise the abdominal wall by producing an overpressure in the body interior and thereby obtain free accessibility to the internal organs.
In abdominal surgery operations surgical instruments, such as forceps, loops and scissors are introduced into the body interior through the trocar sleeve. The actuating or operating members of said instruments are axially oriented in the inoperative position, so that they can be easily introduced through the trocar sleeve. On drawing out operatively removed tissue fragments, e.g. with biopsy or claw forceps, it is standard practice to draw the forceps with the grasped tissue in the not completely closed state and with a varying amount of force into the sleeve, so that the forceps are necessarily closed to the diameter at the distal edge of the sleeve making it possible to draw the forcep mouth with gripped tissue into the trocar sleeve.
As a result the distal end of the sleeve is widened or expanded and then radially projects over the cylindrical trocar, which can lead to a traumatic action, because the widened area can perforate the tissue layers in knife-like manner. The bevelled, distal edge of the sleeve can also become blunt as a result of contact with the actuating members, which is very disadvantageous for a subsequent atraumatic sliding through the tissue, particularly in the case of a Z stitch.
The risk with sleeves soldered into the main body and hitherto normally with soft solder has been that after several uses and multiple sterilizations the soldered joints become brittle and the complete sleeve broke off at the soldered joint. As in the known trocar sleeves the proximal end thereof was almost strictly cylindrical, there was also a risk that in the case of a damaged soldered joint, the sleeve might slide into the interior of the body.
In order to avoid such risks, the one-piece trocar sleeve, i.e. the main body and the sleeve, had to be sent back to the manufacturer, so that the damaged sleeve could be unsoldered from the main body and replaced by a new sleeve. As an untight soldered joint between the sleeve and the main body can lead to a pressure drop in the body interior during the operation and possible complications must be eliminated from the outset, it is necessary to keep in stock a comparatively large number of reserve trocar sleeves. In addition, flexibility was also required with respect to the different trocar sleeve lengths. Moreover, the soldering in and out of sleeves constitutes a considerable cost factor.